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PubMed1987

Role of cyclic AMP in the inhibition of mouse hepatocyte intercellular communication by liver tumor promoters.

The liver tumor promoters phenobarbital (PB) (20-500 micrograms/ml) and 1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane (DDT) (1-10 micrograms/ml) inhibited intercellular communication between primary cultured B6C3F1 mouse hepatocytes after 8 hr of treatment. Intercellular communication was detected autoradiographically as the passage and incorporation of [5-3H]uridine nucleotides from prelabeled donor hepatocytes to recipient hepatocytes. The addition of either dibutyryl cyclic AMP (N6,2'-O-dibutyryladenosine 3':5'-cyclic monophosphate) (0.001-0.1 mM) or caffeine (0.01-1 mM) decreased or completely abolished the inhibitory effects of PB and DDT on intercellular communication. Cyclic AMP (adenosine 3':5'-cyclic monophosphate; cAMP) in primary cultured mouse hepatocytes was measured by radioimmunoassay. Cyclic AMP in nontreated, freshly plated cultures declined from 4.2 +/- 0.7 pmol/mg protein after 1 hr in culture to 2.4 +/- 0.5 pmol/mg protein after 8 hr in culture. Phenobarbital at 250 and 500 micrograms/ml significantly decreased cyclic AMP below control values after 1 hr of treatment. However, no difference in the amount of cyclic AMP was detected between control and PB-treated cultures after 2, 4, and 8 hr in culture or with lower PB concentrations. DDT at 10 micrograms/ml decreased cAMP levels in the hepatocytes after 1, 2, 4, and 8 hr of treatment. No effects were seen after 8 hr of treatment or with lower DDT concentrations. DDT (10 micrograms/ml) also decreased cAMP levels in 24-hr-old cultures while PB (500 micrograms/ml) had no effect. Addition of dibutyryl cAMP (0.1 mM) or caffeine (1.0 mM) to freshly plated cultures elevated cAMP levels 50-fold and twofold, respectively. These data suggest that the inhibition of mouse hepatocyte intercellular communication by PB and DDT at the highest concentrations tested may be mediated by transient decreases in intercellular cAMP levels.

Animals↗
PubMed2002

Comparative effects of phthalate monoesters on gap junctional intercellular communication and peroxisome proliferation in rodent and primate hepatocytes.

Several phthalate esters, compounds used as plasticizers in a variety of commercial products, have been shown to induce hepatic tumors in rodents. In this study, the comparative effects of phthalate monoesters on inhibition of gap junctional intercellular communication and induction of peroxisomal beta-oxidation were assessed in primary cultured hepatocytes from rats, mice, hamsters, cynomolgus monkeys, and humans. A human liver cell line was also utilized. Eight monoesters examined included mono-2-ethylhexyl phthalate (MEHP), mono-n-octyl phthalate (MNOP), mono-isononyl phthalate (MINP, 3 types, -1, -2, and -3), mono-isoheptyl phthalate (MIHP), mono-isodecyl phthalate (MIDP), and mono-(heptyl, nonyl, undecyl) phthalate (M711P). Gap junctional intercellular communication was measured 4 and 24 h after treatment by lucifer yellow dye coupling. Gap junctional intercellular communication was inhibited in rat and mouse hepatocytes by all eight monoesters in a concentration-dependent manner. In most cases, gap junctional intercellular communication was significantly reduced at the lowest concentrations tested (50 pM). Inhibition of gap junctional intercellular communication in rodent cells was substantially reversed within 24 h of monoester removal. In contrast, cell-to-cell communication was not inhibited in hamster, cynomolgus, or human hepatocytes or in a human liver cell line at any concentration examined. In rat hepatocytes, peroxisomal beta-oxidation was elevated after treatment with MEHP, MINP, MIHP, and MIDP but not MNOP or M711P, and with all but MIHP in mouse hepatocytes. The eight phthalates produced no marked change on peroxisomal beta-oxidation in hepatocytes from other species. These data provide additional evidence that the toxicological effects of phthalate esters are species specific.

Adult↗
PubMed1991

Transforming growth factor-beta enhances the extent of intercellular communication between normal rat kidney cells.

Normal rat kidney (NRK) cells cultured in the presence of epidermal growth factor are contact-inhibited at confluent densities. In the additional presence of transforming growth factor (TGF)-beta, however, cells undergo phenotypic transformation which is accompanied by a loss of contact inhibition. In this study, we show by means of the fluorescence photobleaching recovery technique and a scrape-loading dye transfer technique that quiescent confluent cultures of NRK cells do not show extensive gap junction-mediated intercellular communication. Cells contact-inhibited in the presence of epidermal growth factor also show only limited intercellular communication, although with an enhanced permeability coefficient. Cells phenotypically transformed upon addition of TGF beta, however, show extensive intercellular communication, with a similarly enhanced permeability coefficient. This enhanced intercellular communication induced by TGF beta is paralleled by an increase in intracellular pH. It is concluded that in contrast to what has been observed during tumorigenic transformation, phenotypic transformation of NRK cells induced by TGF beta results in an enhancement of the extent of gap junction-mediated intercellular communication.

Animals↗
PubMed2001

Preventive effect of germanium dioxide on the inhibition of gap junctional intercellular communication by TPA.

Gap junctional intercellular communication (GJIC) is thought to be essential for maintaining cellular homeostasis and growth control. In order to detect any protective agent against tumor formation, we examined the anticarcinogenic effect of a germanium dioxide (GeO(2)) using a model system of GJIC in F344 rat liver epithelial cells, named WB cells. 12-O-tetradecanoylphorbol-13-acetate (TPA), known as tumor promoters, inhibited GJIC in the epithelial cells as determined by the scrape loading/dye transfer (SL/DT) assay. And GeO(2) recovered this inhibition of GJIC. Immunostaining of connexin 43 (Cx43) protein in WB cells indicated that TPA caused a loss of Cx43 protein from the cell membranes. However, GeO(2) treatment showed re-appearance of Cx43 protein on the membrane. Reverse transcription-polymerase chain reaction (RT-PCR) and Western blots were analyzed to determine whether the test compounds might have altered the steady-state levels of gap junction mRNA and/or connexin protein levels or phosphorylation. The inhibition of GJIC by TPA in WB cells was correlated with the hyperphosphorylation of Cx43 as measured by mobility shifts of the western blot bands of Cx43. TPA induced hyperphosphorylation of Cx43 protein, while GeO(2) appeared to partially block this hyperphosphorylation. Here, we showed that pre- and co-incubation with GeO(2) in TPA-treated WB-cells abolished down-regulation of GJIC by TPA. These data suggest that GeO(2) may inhibit tumor promotion by enhancing GJIC.

Animals↗
PubMed1989

[Evaluation of intercellular communication of human prostatic epithelium].

Intercellular communication (IC) among epithelial and/or interstitial cells of human prostate was evaluated. IC was measured by the dye transfer method. In brief, fluorescent lucifer yellow CH was microinjected into an individual cell and communication was measured by scoring the number of surrounding fluorescent cells. Cells used here were outgrowth cells from small tips of tissues of various prostatic diseases and established prostatic carcinoma cell line PC-3. To identify the epithelial cells, keratin staining was done. In prostatitis and benign prostatic hyperplasia, epithelial cells grew in five of six cases cultured and extent of maximum IC was from 18 to 46 cells (mean = 26 cells) at 4 to 6 culture days. Three specimens of separate cases cultured for more than one month had a maximum IC of more than 100 cells. In prostatic carcinoma, epithelial cells grew in 7 of 10 cases cultured and extent of maximum IC was from 6 to 38 cells (mean = 18 cells) at 3 to 6 days. The extent of IC among prostatic carcinoma cells was lower than that of benign prostatic diseases, though not significantly, this indicates the possibility that benign cells were present among the malignant cells in the specimens examined above. Prostatic carcinoma cells cultured from metastatic lesions of bone (PC-3) and lymph nodes had maximum IC of 3 to 5 cells. IC was very limited or absent between benign prostatic epithelium and PC-3 cells. No IC was present between prostatic epithelial and interstitial cells. Interstitial cells prepared from prostatic benign and malignant diseases similarly revealed a high extent of IC.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Communication↗
PubMed1997

[Effect of interleukin-1, interleukin-6 on the intercellular communication of rat thyroid FRTL-5 cells].

We observed the effects of thyrotropin (TSH), interleukin (IL)-1 beta and IL-6 on the intercellular communication of FRTL-5 cells with fluorenscence redistribution after photobleaching (FRAP) analysis. FRTL-5 cells were cultured and exposed to the different concentrations of TSH, IL-1 beta and IL-6 for 12 hours. The mean fluorescence recovery rate (MFRR, %/min) of the cells labelled with carboxyfluocein diacetate (CFDA) after photobleaching was measured with laser scanning cytometry. The MFRR (%/min) of the cells after exposure to TSH was 0.445 +/- 0.033 at the control group, 0.679 +/- 0.054 at the group of 0.1 U/L, 0.950 +/- 0.073 at the group of 1 U/L, and 0.799 +/- 0.082 at the group of 5 U/L, respectively (F = 11.44, P < 0.01). The indicated that TSH could enhance the intercellular communication of FRTL-5 cells. The MFRR after exposure to IL-1 beta was 0.564 +/- 0.032 at the control group, 0.485 +/- 0.042 at the group of 10(3) U/L, 0.445 +/- 0.043 at the group of 10(4) U/L and 0.405 +/- 0.029 at the group of 10(5) U/L, respectively (F = 3.58, P < 0.01). The suggested that IL-1 beta could inhibite the intercellular communication of FRTL-5 cells. IL-6 had no obvious effect on the intercellular communication of FRTL-5 cells.

Animals↗
PubMed2002

Bone morphogenetic protein-2 modulation of chondrogenic differentiation in vitro involves gap junction-mediated intercellular communication.

Undifferentiated mesenchymal cells in the limb bud integrate a complex array of local and systemic signals during the process of cell condensation and chondrogenic differentiation. To address the relationship between bone morphogenetic protein (BMP) signaling and gap junction-mediated intercellular communication, we examined the effects of BMP-2 and a gap junction blocker 18 alpha glycyrrhetinic acid (18alpha-GCA) on mesenchymal cell condensation and chondrogenic differentiation in an in vitro chondrogenic model. We find that connexin43 protein expression significantly correlates with early mesenchymal cellular condensation and chondrogenesis in high-density limb bud cell culture. The level of connexin43 mRNA is maximally upregulated 48 h after treatment with recombinant human BMP-2 with corresponding changes in protein expression. Inhibition of gap junction-mediated intercellular communication with 2.5 microM 18alpha-GCA decreases chondrogenic differentiation by 50% at 96 h without effects on housekeeping genes. Exposure to 18alpha-GCA for only the first 24-48 h after plating does not affect condensation or later chondrogenic differentiation suggesting that gap junction-mediated intercellular communication is not critical for the initial phase of condensation but is important for the onset of differentiation. 18alpha-GCA can also block the chondrogenic effects of BMP-2 without effects on cell number or connexin43 expression. These observations demonstrate 18alpha-GCA-sensitive regulation of intercellular communication in limb mesenchymal cells undergoing chondrogenic differentiation and suggest that BMP-2 induced chondrogenic differentiation may be mediated in part through the modulation of connexin43 expression and gap junction-mediated intercellular communication.

Animals↗
PubMed2005

Suberoylanilide hydroxamic acid enhances gap junctional intercellular communication via acetylation of histone containing connexin 43 gene locus.

A histone deacetylase (HDAC) inhibitor, suberoylanilide hydroxamic acid (SAHA), induces apoptosis in neoplastic cells, but its effect on gap junctional intercellular communication in relation to apoptosis was unclear. Therefore, we carried out a comparative study of the effects of two HDAC inhibitors, SAHA and trichostatin-A, on gap junctional intercellular communication in nonmalignant human peritoneal mesothelial cells (HPMC) and tumorigenic ras oncogene-transformed rat liver epithelial cells (WB-ras) that showed a significantly lower level of gap junctional intercellular communication than did HPMC. Gap junctional intercellular communication was assessed by recovery rate of fluorescence recovery after photobleaching. Treatment of HPMC with SAHA at nanomolar concentrations caused a dose-dependent increase of recovery rate without inducing apoptosis. This effect was accompanied by enhanced connexin 43 (Cx43) mRNA and protein expression and increased presence of Cx43 protein on cell membrane. Trichostatin-A induced apoptosis in HPMC but was less potent than SAHA in enhancing the recovery rate. In contrast, treatment of WB-ras cells with SAHA or trichostatin-A induced apoptosis at low concentrations, in spite of smaller increases in recovery rate, Cx43 mRNA, and protein than in HPMC. Chromatin immunoprecipitation analysis revealed that SAHA enhanced acetylated histones H3 and H4 in the chromatin fragments associated with Cx43 gene in HPMC. These results indicate that SAHA at low concentrations selectively up-regulates Cx43 expression in normal human cells without induction of apoptosis, as a result of histone acetylation in selective chromatin fragments, in contrast to the apoptotic effect observed in tumorigenic WB-ras cells. These results support a cancer therapeutic and preventive role for specific HDAC inhibitors.

Acetylation↗
PubMed1989

Association of decreased intercellular communication with the immortal but not the tumorigenic phenotype in human mammary epithelial cells.

Intercellular communication was compared in early passage cultures of human mammary epithelial cells (HMEC) from normal and malignant breast tissues and immortalized nontumorigenic human breast cell lines (184A1 and 184B5). A clonogenic assay for the cell-mediated transfer of toxic metabolites of 6-thioguanine (TG) between cells was used as a measure of intercellular communication. We examined the effects of wild-type TG-sensitive (TGs) HMEC density on the survival of mutant TG-resistant (TGr) immortalized HMEC in TG-containing medium. Survival rates of TGr HMEC cocultured with TGs normal HMEC, malignant HMEC, or immortalized nontumorigenic HMEC were dependent on the density of TGs cells. For example, the percentage of recovery of TGr cells cocultured with 10(5) TGs immortalized, normal, or carcinoma HMEC was 88 +/- 4, 41 +/- 10, or 2.0 +/- 1.7, respectively. Gap junction-mediated intercellular communication between homologous HMEC types was also studied, as quantitated on the basis of Lucifer yellow dye transfer between cells in culture. Results from the dye transfer studies supported those from the metabolic cooperation studies. These results using nonimmortalized tumor cells differ from previous reports in which immortal tumor cells have been found to communicate less than their normal counterparts. Previous reports suggesting that tumor cell lines communicate less than normal cells may have resulted from the confounding influence of the immortal phenotype on the tumor phenotype.

Breast↗
PubMed2003

Characterization of gap junctional intercellular communication in immortalized human pancreatic ductal epithelial cells with stem cell characteristics.

INTRODUCTION: Gap junctional intercellular communication has been implicated in the homeostatic regulation of cell growth, differentiation, and apoptosis. Cancer cells, which have been viewed as "partially blocked stem cells," and which lack the ability for growth control, terminal differentiation, and apoptosis, also lack functional gap junctional communication. AIMS AND METHODOLOGY: A clone of a human pancreatic ductal epithelial cell line, H6c7, derived after immortalization with human papilloma virus, was used to examine gap junctional intercellular communication and the ability to differentiate under different growth conditions. RESULTS: The cells showed characteristic epithelial morphology on standard tissue culture dishes. When placed on Matrigel they showed phenotypical changes with extensive ductal organization and budding structures. In growth medium containing hormones and growth factors, these cells were gap junctional intercellular communication (GJIC)-incompetent. In the presence of c-AMP elevating agents, isobutylmethylxanthine, and forskolin, in basal medium that did not contain the hormones and growth factors, the cells became GJIC-competent and expressed connexin43 gap junction protein within 48 hours after treatment. RT-PCR analyses of the cells under different growth conditions showed that the cells expressed, and genes when cultured in the basal medium with c-AMP elevating agents. They also expressed the gene that did not change with c-AMP treatment. H6c7 cells also have the capacity to turn on an ectopic insulin promoter reporter gene. CONCLUSION: Our data suggest that the immortalized H6c7 cells retain stem-like characteristics and have the potential to differentiate into duct-like structures and perhaps insulin-producing cells.

Cell Communication↗
PubMed1996

Intercellular communication in the bovine corpus luteum.

There is a growing body of evidence that intercellular communication is important in the regulation of luteal function. Although the nature of the interactions between small and large luteal cells are not yet clear, it seems likely that they do exist. Many of the substances to which luteal cells respond, such as prostaglandins, growth factors, oxytocin and progesterone, are produced locally. These substances may act as paracrine factors to modulate the response of luteal cells to hormonal signals. Endothelial cells also produce factors that can modify steroidogenesis, and luteal cell-stimulation of endothelial cell proliferation is necessary for the extensive angiogenesis that occurs during luteinization Finally, bidirectional intercellular communication likely occurs between luteal cells and resident immune cells. Immune cells produce cytokines that can modify progesterone and prostaglandin synthesis by luteal cells. Cytokines may also have direct cytotoxic effects on luteal cells, and dead cells are then phagocytized by resident macrophages. Also, factors secreted by luteal cells can serve as chemoattractants for immune cells, and can enhance or suppress immune cell functions. There is little doubt that intercellular communication within the corpus luteum is very complex. One must remember, however, that nearly all evidence collected thus far is based on in vitro studies. Eventually, technology will allow for study of these interactions in vivo, and may lead to new methods for control of luteal function.

Journal Article↗
PubMedDate not supplied

[Intercellular communication].

There are 3 modalities for intercellular communications: the chemical substances secreted by some cells are transported at distance where they act as signals on other cells; the surface molecules of a group of cells interact with the neighbouring cells; some special junctions or nexus provide direct relations between cells. In the first modality the chemical signals operate in 3 ways: a) many cells secrete one ore more chemical signals which act as local mediators (paracrine model); these mediators act immediately or are destroyed after they influence the neighbouring cells; b) some specialised cells--endocrine cells--secrete hormones, which are liberated in small amounts into the blood and exert their effects on some target cells, able to recognise and to respond to the hormonal signal; c) the neurones secrete chemical mediators--neurotransmitters, which act at the level of some special junctions--the chemical synapses. Most biologic phenomena are under the overlapping control of both systems--thus they are regarded as neuroendocrine system. The nervous cells transmit the informations much more rapidly than the endocrine cells. The chemical signals are various, as regarding the structure and function: they are large polypeptides, small polypeptides, glycoproteins, amino-acids, steroid molecules derived from cholesterol and fatty acids. The ability of the cells to respond to an extracellular signal molecule depends on the existence of some specific proteins, included in the plasma membrane, called receptors. The chemical signals influence the target cells both by altering the properties or the synthesis rate of their own proteins or by initiating the synthesis of new proteins. The chemical signals induce rapid and transient or slow- and long-lasting responses. All the neurotransmitters and the majority of hormones are water-soluble; the steroid and thyroid hormones are relatively water insoluble; the mechanisms of influencing the target cells are dependent of this feature: the water-soluble molecules do not pass through the target cell membrane, they bind to the surface specific receptor while the insoluble molecules cross the plasma membrane of the target cell and bind to the cytoplasmatic receptors. It results that the water-soluble molecules mediate short-time responses while those insoluble--long-lasting responses. As regarding the local chemical mediators they are secreted by mast cells or they are represented by the large category of prostaglandins. They produce a great diversity of biological effects, they are rapidly destroyed, and this way, they don't penetrate into the blood stream in significant amounts. The majority of the receptors from the surface of activated cells generate some intracellular signals both by altering the activity of some membrane enzyme (adenilate cyclase) with the accumulation of cyclic MPA and by modifying the permeability of some membrane channels(Ca2+ channels). The target cell exposed to a signal for a long period of time loose often the ability to respond to this signal. This process called desensibilization is reversible and is explained by endocytosis of surface receptors together with the ligand and by their lysosomal destruction, by the degradation of the receptor molecular conformation which becomes unable to bind the ligand or by the lack of activation of membrane enzymes or the channels. The gap or nexus junctions are composed by some proteic particles which form a hydrophilic channel to assure the communication between 2 neighbouring cells. These junctions allow some molecules (amino-acids, monosaccharides, cAMP, nucleotides) to pass from a cell to another one, facilitating the chemical and electrical coupling. These structures show a low electrical resistance, but they are dynamic, some junctions have the capacity to change from a low resistance to a high resistance state, isolating the cells from communicating with their neighbours. Oxygen deprivation, the increase of intracellul

Animals↗
PubMed1985

Gap junctions and direct intercellular communication between rat uterine smooth muscle cells.

We have tested the hypothesis that an increase in direct intercellular communication accompanies the development of gap junctions (GJs) between rat uterine smooth muscle cells at parturition. Intercellular communication in these tissues was studied by exposing one portion of small strips of myometrium to 2-[3H]deoxy-D-glucose (2-DG) and determining the longitudinal distribution of tracer after a 5-h period of diffusion. The distribution of 2-DG was greater in parturient compared with ante- and postpartum tissues. Similarly, the apparent diffusion coefficient of 2-DG was almost 10-fold greater in delivering tissues (1.86 X 10(-6) cm2/s) than before (0.199 X 10(-6) cm2/s) or after (0.296 X 10(-6) cm2/s) parturition. Control experiments indicated that the redistribution of 2-DG was dependent on the presence of GJs and was the result of intracellular and direct cell-to-cell diffusion. The appearance of GJs is the myometrium at term facilitates direct intercellular communication between uterine smooth muscle cells during labor. This improved communication may be responsible for synchronizing and coordinating electrical, metabolic, and contractile activity in the uterine wall and, hence, the effective expulsion of fetuses.

Animals↗
PubMed2002

Connexins, gap junctional intercellular communication and kinases.

A number of kinases and signal transduction pathways are known to affect gap junctional intercellular communication and/or phosphorylation of connexins. Most of the information is available for protein kinase A, protein kinase C, mitogen-activated protein kinase, and the tyrosine kinase Src. Much less is known for protein kinase G, Ca(2+)-calmodulin dependent protein kinase, and casein kinase. However, the present lack of knowledge is not necessarily synonymous with lack of importance in the regulation of intercellular communication and phosphorylation of connexins. Kinases and the phosphorylation of connexins may be involved in the regulation of gap junctional intercellular communication at all levels ranging from the expression of connexin genes to the degradation of the gap junction channels. The exact role of the phosphorylation depends both on the kinase and the connexin involved, as well as the cellular context.

Animals↗
PubMed1999

Phosphatases involved in modulation of gap junctional intercellular communication and dephosphorylation of connexin43 in hamster fibroblasts: 2B or not 2B?

12-O-Tetradecanoylphorbol-13-acetate (TPA) caused strong suppression of gap junctional intercellular communication, altered phosphorylation status of the gap junction protein, connexin43, and disappearance of immunorecognizible connexin43-containing gap junction plaques in V79 fibroblasts. When TPA was removed, all parameters normalized during a 3- to 4-h period. The normalizations were independent of protein synthesis, suggesting the possible involvement of phosphatases. None of the phosphatase inhibitors okadaic acid, calyculin A, cyclosporin A, or FK506 affected intercellular communication or connexin43 phosphorylation status on their own. In sequential exposures to TPA and phosphatase inhibitors, only the protein-phosphatase 2B (PP2B) inhibitors cyclosporin A and FK506 delayed the recovery of the studied parameters. Rapamycin binds to the same set of proteins as does FK506, but without inhibiting PP2B. Rapamycin did not affect the recovery of intercellular communication, but it delayed the normalization of connexin43 band pattern and immunorecognition of gap junction plaques. Dephosphorylation of immunoprecipitated connexin43 was studied using PP1, 2A, 2B, and 2C. PP2A was the most efficient (by 100-fold on a molar basis). Connexin43 immunoprecipitated from TPA-exposed cells was a poor substrate for PP1, 2B, and 2C. Thus, PP2B appeared to play a role in normalization of intercellular communication, but not necessarily in direct dephosphorylation of connexin43. Peptidyl-prolyl isomerase activity of cyclosporin/FK506/rapamycin-binding proteins may promote the dephosphorylation of connexin43 in cells.

Animals↗
PubMed2002

Quantitative analysis of gap-junctional intercellular communication in precision-cut mouse liver slices.

Direct intercellular communication through gap junction channels is involved in the maintenance of tissue homeostasis and suppression of carcinogenesis. Gap-junctional communication is often altered in tumor cells but it can also be modulated in response to tumor promotors or inflammatory signals. In order to evaluate the effect of nongenotoxic compounds, suggested to be involved in tumor promotion, on gap junctional intercellular communication in the liver, we have developed a direct dye transfer method. The fluorescent dye Alexa Fluor 488 was iontophoretically injected into hepatocytes of freshly prepared, precision-cut mouse liver slices (250 microm). The area of dye spreading was monitored and quantified by microscopy. Comparison of dye spreading in connexin-32-deficient versus wild-type liver revealed a 96% decrease in connexin-32-deficient tissue. Induction of an acute phase response in connexin-32-deficient mice by intraperitoneal injection of lipopolysaccharide increased dye coupling by 33%, probably due to upregulation of connexin-26-containing gap junction channels.

Animals↗
PubMed1988

Effects of sodium L-ascorbate, uracil, butylated hydroxyanisole and extracellular pH on junctional intercellular communication of BALB/c 3T3 cells.

To study the mechanism of tumor promotion by different classes of urinary bladder promoters, the effect of sodium L-ascorbate, uracil and butylated hydroxyanisole (BHA) on junctional intercellular communication was examined in cultured BALB/c 3T3 cells using a dye-transfer method. In addition, since administration of sodium L-ascorbate and several other bladder tumor promoters is known to result in increased urinary pH, the effect of pH of the culture medium on intercellular communication was investigated. Results showed that under the present experimental conditions on the BALB/c 3T3 cells, BHA inhibited intercellular communication while sodium L-ascorbate and uracil did not. Intercellular communication was inhibited in proportion to the increase of medium pH after incubation of 4 h. Although further study is necessary to confirm the negative results of sodium L-ascorbate and uracil, these results suggest differences in the promoting mechanism(s) among these agents.

Animals↗
PubMed1995

Reversible inhibition of gap junctional intercellular communication, synchronous contraction, and synchronism of intracellular Ca2+ fluctuation in cultured neonatal rat cardiac myocytes by heptanol.

We analyzed by Fotonic Sensor, a fiber-optic displacement measurement instrument, the effects of heptanol on synchronized contraction of primary neonatal rat cardiac myocytes cultured at confluent density. We also examined the effect of heptanol on the changes in gap junctional intercellular communication by using the microinjection dye transfer method, and on intercellular Ca2+ fluctuation by confocal laser scanning microscopy of myocytes loaded with the fluorescent Ca2+ indicator fluo 3. In addition, we studied expression, phosphorylation, and localization of the major cardiac gap junction protein connexin 43 (Cx43) using immunofluorescence and Western blotting. At Day 6 of culture, numerous myocytes exhibited spontaneous, synchronous contractions, excellent dye coupling, and synchronized intracellular Ca2+ fluctuations. We treated the cells with 1.5, 2.0, 2.5, and 3.0 mmol/liter heptanol. With 1.5 mmol/liter heptanol, we could not observe significant effects on spontaneous contraction of myocytes. At 3.0 mmol/liter, the highest concentration used in the current experiment, heptanol inhibited synchronous contractions and even after washing out of heptanol, synchronous contraction was not rapidly recovered. On the other hand, at the intermediate concentrations of 2.0 and 2.5 mmol/liter, heptanol reversely inhibited synchronized contraction, gap junctional intercellular communication, and synchronization of intracellular Ca2+ fluctuations in the myocytes without preventing contraction and changes of intracellular Ca2+ in individual cells. Brief exposure (5-20 min) to heptanol (2.0 mmol/liter) did not cause detectable changes in the expression, phosphorylation, or localization of Cx43, despite strong inhibition of gap junctional intercellular communication. These results suggest that gap junctional intercellular communication plays an important role in synchronous intracellular Ca2+ fluctuations, which facilitate synchronized contraction of cardiac myocytes.

Alcohols↗